WHY DOES RUSSIA CELEBRATE ITS NATIONAL DAY ON JUNE 12?

Russia Day, the national holiday of the Russian Federation, has been celebrated on June 12 every year since 1992.

The First Congress of People's Deputies of the Russian Federation adopted the Declaration of State Sovereignty of the Russian Soviet Federative Socialist Republic on June 12, 1990.

The creation of the Presidency, the adoption of the new Russian Constitution, flag, anthem and emblem were major landmarks in the consolidation of Russian statehood.

The day when the declaration was adopted- June 12 - was proclaimed as national holiday by Supreme Soviet of Russia in 1992.

Russia's first President, Boris Yeltsin, was also elected on the same day in 1991.

Edyta Galazkowska, spokesman for Warsaw ambulance service, said 14 Russians, one German, one U.S. citizen and one Pakistani were among the injured.

The nationality of seven others was being established. None was in life-threatening condition.

A Warsaw police spokesman added: 'We are still monitoring the situation and trying to identify the supporters involved.

'The operation is not over from our side as we continue in our attempts to catch those who are causing trouble.'

Tensions were already running high with home fans having mocked the Russians over a Polish army victory in 1920.

The two countries are uneasy neighbours with Russia having occupied Poland for more than a century and dominating the country after the Second World War.

Football governing body UEFA has already begun disciplinary proceedings against Russian fans caught on film kicking and punching stewards near a walkway at the Wroclaw stadium after their side beat the Czech Republic 4-1.

Police and fans clash during a march of Russian supporters to the National Stadium in Warsaw

An injured Russian fan is seen as Polish and Russian fans clash ahead of the two nations' clash in the European Championships

More fans from both sides clash ahead of the match between Poland and Russia

There were a number of other incidents as well, which came as Russia fans waving their country's flag marched to the stadium in a show of patriotism seen as provocative to many Poles.

It was considered a huge security challenge for police. Russia fans clashed with police on a bridge near the National Stadium and police were later seen making arrests.

In another incident, a group of clearly drunken Polish men began fighting among themselves, hitting and kicking each other.

Two were on the ground bleeding and police intervened, throwing two more to the ground.

The men were holding cans of beer and mumbling and one appeared to be unconscious. An AP reporter witnessed the incident and saw police detain three people.

One Russian who didn't have tickets to the game, but made the two-day car trip from Moscow simply to be in be the city, said it was wrong for the Russians to march in Warsaw given the countries' troubled history.

Riot policemen stand guard during the match between the two nations

Pitch battle: Polish armed officers take up their positions on the sidelines ahead of last night's match between Poland and Russia

Clampdown: Stewards carry away a Russian who ran on the pitch after the game

Heated: The players themselves even got involved in some tempestuous exchanges on the pitch

'The march, it wasn't right. It was a provocation. It shouldn't happen like this. But there are also aggressive Poles and we are scared here,' said the man, who gave only his first name, Petya.

He and a friend had hoped to cross a bridge leading from the city center to the stadium to soak up the atmosphere in the area.

But they gave up that notion and were sitting outside, sipping on beers from a distance, and planning to watch the match on TV in an apartment with friends.

In recent days, Polish media have tried to stir up nationalistic sentiments over the match, suggesting the encounter would be more than a simple soccer game.

Newspapers on Monday were full of dramatic references to Poland's victorious 1920 battle against the Bolshevik Army, known as the Miracle on the Vistula.

The Super Express tabloid carried a front page mocked-up picture of Poland coach Franciszek Smuda charging on horseback, saber in hand, in a 1920 Polish army uniform under the headline "Faith, Hope, Smuda" - a play on an old army motto: "Faith, Hope, Motherland."

Fans cross the Poniatowski Bridge after the1-1 draw between Russia and Poland

A Polish fan stands up to a line of riot police as trouble in Warsaw continued into the evening

Officers prepare to fire rubber bullets as the trouble threatened to get out of hand following the game